One current technique for treatment of certain kinds of back injuries is to attach one or more rigid rods to a person's vertebra using screws which have been coupled to the one or more vertebra by threading into the bone. A tulip is coupled to a head of the screw. The rod is connected to the tulip and is secured in position on the tulip by one or more different types of fasteners.
Tulips currently available in the art are relatively large and obtrusive. For example, the tulip disclosed in U.S. Pat. No. 5,882,350 shows a large clamp member (24) coupled to a tulip (22), as shown in FIG. 1. A collet (14) may have one or more slots (18) to hold the tulip (22) on the head (12) of the screw (16). Another example of a rod and pedicle screw assembly is shown in U.S. Pat. No. 6,402,752, of which two figures are shown in FIGS. 2 and 3, respectively. These three figures show a rod (20) coupled to the head (12) of the screw (16). The tulip (22) has a top region (24) which aids in connecting the rod (20) to the head (12) of the screw (16). One or more side plates (26, 28) together with additional members (30, 32) assist in rigidly connecting the rod (20) to the screw (16). As can be seen in FIGS. 2 and 3, the tulip (22) extends a substantial distance above the head (12) of the screw (16). This results in a larger and more obtrusive pedicle screw assembly which increases both the tissue damage during surgery and recovery time needed after surgery.
Additionally, these and other conventional pedicle screw systems that are rather large and bulky may result in more tissue damage in and around the surgical site when the pedicle screw system is installed during surgery. The prior art pedicle screw systems have a rod-receiving device that is pre-operatively coupled or attached to the pedicle screw. In addition, some of the prior art pedicle screw systems include numerous components that must all be carefully assembled together. Further, traditional pedicle screw systems are pre-operatively assembled, which makes these systems more difficult to install and maneuver in a spinal operation where MIS techniques are used.